It is now possible to put on a single piece of semiconductor, millions of devices running at clock frequency values expressed in hundreds of megahertz or even gigahertz for some electronic components. These devices, such as resistors, capacitors, transistors, and integrated circuits are what power many of today's consumer electronics, such as cellphones, video cameras, portable music players, computers, etc. Unfortunately, many of these devices emit or are susceptible to undesirable energy disturbances, such as electromagnetic (EM) and radio frequency (RF) interference. For example, a device that emits electromagnetic or radio frequency signals may adversely impact neighboring electronic components and devices. Consequently, the electronics industry has sought solutions for shielding these electronic components and devices from emitting or receiving disruptive energy signals.
Several methods are available for protecting and shielding one or more electronic components from EM and RF interference. One method of protecting an electronic component from emitting such emissions is to provide a shield, which serves to shield an area of the printed circuit board(s), or a volume associated therewith. The shield functions by either containing EM energy, e.g., radiated RF signals, within a shielded volume or area or the electromagnetic energy is excluded by the shield structure from the shielded volume or area.
Such shielding is extensively used in television receivers, direct satellite broadcast receivers, radio receivers such as FM and short-wave, or portions of audio systems, wherein low signal level circuitry is amenable to being effected by stray electromagnetic fields emanating from alternating current (AC) power sources.
A printed circuit board (PCB) is a common electronic substrate to which a shield can be applied since PCBs enjoy widespread use in a number of electronic applications. The term “printed circuit board” generally refers to circuit boards having electrical conductors disposed on one or more side of a substrate (e.g., a dielectric substrate). Often a PCB will have openings or via formed through the substrate to receive electrical leads of an electronic component that is mounted on one side of the PCB. The electrical leads extend through the openings to contact pads disposed on the other side of the PCB. The leads are typically soldered to the contact pads.
There are several techniques for mounting the shield to the PCB. One technique is to directly solder the shield to a ground plane of a PCB that is proximate to EM and RF emitting components. Another technique involves the use of shield clips coupled to the ground plane of a PCB to which a shield is permanently attached. Another technique involves the use of removable shields attached to shield clips coupled to the ground plane of the PCB.
For the most part, the shields totally encompass the semiconductor components and this presents a problem when both the semiconductor components and the shields are to be embedded in an encapsulant to form a protective package system. In order to have free entry of the encapsulant, however, there must be openings in the shields, but openings in the shields provide escape paths for EM and RF interference.
Thus, a need still remains for an integrated circuit package system that prevents transmission of disruptive electromagnetic energy, but yet still allows for easy encapsulation of a semiconductor component located within a shield. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.